Here is the full list of all 20 The Clans - there are Saga of the Twins achievements.
Defeat the Guardian Spirits.
Defeat the final boss.
Defeat the final boss on the Ahaha difficulty level.
Defeat the turtles.
Defeat Demon Master.
Defeat Skeletard.
Get rewarded by Sachiko.
Defeat Ex-Mayor.
Defeat Stone Guardian.
Defeat Project X
Defeat Bob the Crimson Spider.
Beat the 15th Testing Chamber.
Defeat Alpha Omega.
Defeat the Alpha Omega on the Ahaha difficulty level.
Defeat Chimera.
Defeat Onyxus.
Defeat Tormentor.
Loot a chest.
Win a battle.
Exit the bar.